THE QUESTION OF FUEL
PART I - Thinking Of Mixing Your Own Fuel? Better Think Again.
Mixing Fuel Is Dangerous Business

By John Copeland

The question of fuel tampering has plagued karting for decades, and for all the efforts by sanctioning bodies and tech officials, we're no closer to a workable solution than we were in the 1960s. Those with the knowledge and the resources to circumvent the testing procedures have enjoyed an unfair advantage over their competitors. But fooling around with fuel isn't just unfair, it's dangerous. Few karters have the background in fuel chemistry to approach the task of getting more power in a logical, educated manner. Most just try a little of this and a little of that, mostly additives that they've heard about somebody else using, and hope for the best. The guy who said "A little knowledge is a dangerous thing" must have been talking about mixing up fuel. Maybe the best way to begin is to clear up some of the misinformation about fuel and additives and how they work.

We have to begin by understanding that all the horsepower our engines are ever going to make are stored in the fuel. It's that simple. The specific energy content of the fuel/air mixture is the key. The more fuel energy your engine can EFFICIENTLY burn, the more power it will produce. A lot of factors influence this fuel energy: gross volume, air/fuel ratio, density of the mixture, completeness of vaporization, and flame speed. You'll notice we didn't mention octane rating. That's because, in and of itself, octane rating does nothing to improve power output. All octane rating does is measure the ability of a fuel to resist pre-ignition (also called detonation).

Higher octane fuels allow the use of higher compression ratios, and THAT produces more power. However, Yamahas, Piston Ports and Controlleds that have cc limits called out in tech that can't even begin to approach the compression ratios to take advantage of high octane fuel, While an octane rating does influence flame speed, so do other factors. Let's look at each of the other factors individually.

Vaporization is just what it sounds like: how well is the fuel/air mixture dispersed at the point of ignition. Incompletely atomized fuel burns more slowly and may not burn completely. It doesn't do you any good if it isn't completely consumed by the time the exhaust port opens.

The better a job you can do in getting a uniform dispersion of fuel in the incoming air, the more completely it will burn. There are a number of additives that act to reduce the surface tension of gasoline and aid its vaporization. Unfortunately, most oils in common use have relatively high surface tension in solution with gasoline and so inhibit the vaporization process. Most gasoline manufacturers already add detergent-like additives to their fuel, so this ground has already been covered.

Flame speed is also pretty self-explanatory, but there are two sides to this coin. On one hand, the faster the fuel/air mixture burns, the higher expanding gas pressure will be and the longer the pressure will have to work on the piston before the exhaust port opens. However, since the ignition system is timed to fire before the piston reaches top-dead-center, some of that gas pressure will actually work AGAINST the piston as it completes the compression stroke. They call it "knock" in your family car, but it's really pre-ignition and it can be really destructive. It can literally chew the top of a piston away a little bit at a time. In less then a minute, at the RPM that today's two cycles run the top of the piston is gone and you're done. In extreme cases, pre-ignition can break pistons, and the damage that it can do is impressive (and expensive).

Higher octane fuels, in general, burn more slowly than low octane fuels, but other additives that have little or no bearing on octane rating can affect flame speed.

The density of the fuel/air mixture is the subject of a great deal of interest throughout the racing world. The cooler the charge of fuel and air going into the engine, the denser it will be. And the denser it is, the more potential energy there is in each incoming charge.

Remember that all the horsepower you're going to get is stored in that fuel and air, so the denser a charge you can get into the engine, the better. Superchargers and turbochargers increase the charge density mechanically by compressing it, but that generates a lot of heat in the mixture before it ever gets into the cylinder.

Consequently, more and more "boosted" engines use intercoolers, radiators that cool the mixture and make it denser before it gets to the combustion chamber. Chilling the fuel in the tank has some merit, but with the simple carburetors that karts use, maintaining that desired fuel/air ratio becomes extremely difficult if you begin to fiddle with the temperature of the incoming fuel. It's much more efficient to use fuel additives that have high heat of vaporization to cool the charge. All liquids absorb heat energy when they change from a liquid to a gaseous state, that's how the freon in a refrigerator works. When a liquid is vaporized, like your fuel going through the carb and into the air stream, it gets colder. That cools the air it mixes with and the resulting fuel/air charge gets denser. Neat, huh? Well, different liquids have different heats of vaporization. Alcohols have a substantially higher heat vaporization than gasoline (ever notice how cold it gets if you get some on your hand?), but other highly volatile options exist. In general, hydrocarbons with lower boiling points will have higher heats of vaporization.

Fuel/air ratio is really two subjects. First of all, and familiar to all of us, is the ratio that we can adjust at the carburetor. There is, of course, an optimum ratio of gasoline to air for most efficient combustion. This ratio is generally agreed to be approximately 7:1, 7 pounds of fuel to 1 pound of air. Unfortunately, for most of us, the restrictions of running air-cooled engines make it impossible to approach that ratio. Instead, we pour substantially more fuel through our engines as a COOLANT.

That's right, some detailed computer modeling in the '60s indicated that almost 50 percent of the fuel passed through an air cooled two-cycle engine was not consumed in combustion, but rather its vaporization within the cylinder leeched heat away. (See heat of vaporization above) That's why all the factory motorcycle racers are water-cooled now, and why those water-cooled gearbox karts are so much quicker than their air-cooled cousins. They can simply run leaner fuel/air ratios that more closely approach the optimum ratio. The goal at the carburetor is to get the leanest ratio that the engine's cooling capability will tolerate.

T h e larger, and substantially more complex side of the fuel/air ratio, issue is how that ratio changes with different fuels and additives. The theoretical optimal fuel/air ratio for methanol, for example, is approximately 18:1, as opposed to 7:1 for gasoline described above.

Nitroparaffins like nitromethane, nitropropane, and others are more like 70:1. That's 10 TIMES MORE FUEL for a given amount of air to burn correctly. What this means to the fuel mixer is this; as you adjust the chemical content of the fuel, you may substantially change the volume of fuel that the carb is required to mix for the engine to perform correctly. Legality not withstanding, adding enough of these sorts of additives to generate a noticeable improvement in performance will likely require substantial modifications of the passages in the carburetor to accommodate the volume of fuel required. Percentages small enough not to exceed the carb's ability to deliver fuel will not provide enough improvement in power to be measurable.

Most of the commonly used fuel additives actually have a lower specific energy content per unit volume than racing gasoline. But their higher optimal fuel/air ratio (called the stoichiometric ratio) more than makes up for the lower energy per volume with a lot more volume. Gasoline could be accurately described as a chemical "vegetable soup," containing dozens of chemical compounds. Fuel chemists at every major oil company are constantly fiddling with the composition of their products in effort to stay on top of the market. Cleaner burning, lower emissions, and better fuel mileage are at the top of their priority list, but they're also interested in things like stability for long-term storage, low VOC emission for handling, and other factors. Primarily, gasoline is a blend of several chemical families, including, but not limited to, Alkanes, also known as paraffins, Iso-Alkanes like iso-octane and triptane Cycloalkanes (napthenes), Alkenes (olefins), and Aromatics like benzene and toluene.

Varying the ratios of these ingredients will modify the characteristics of the gasoline. To these
basic building blocks the fuel chemists add an ever-increasing variety of modifiers to minimize gum formation to prevent metal iron migration from handling equipment, and to accomplish lots of other goals. Many pump gasolines are now "seasonally adjusted" with
alcohols, ethers, and other products to improve their performance in varying weather conditions.

Racing gasoline is, in general, not subject to as much chemical monkeying around. Pump gasolines, with their constantly changing composition, is risky business, legality-wise. Just because a certain grade of pump gas from a certain pump passed tech for the last 10 years, is no guarantee that it will pass tomorrow. This is not necessarily because the test has changed, but because the gas may have.

In upcoming months we'll take a look at several of the more commonly used fuel additives; what they're supposed to do for you, and what the pluses and minuses are. We'll also look at how they react to different methods of fuel tech, both the old standards like the Digatron meter and water test, and some of the newer, more sophisticated testing procedures. We'll hopefully unravel some of the mysteries and myths about fuel additives. And when its over, we'll look down the road a bit and see if we can see where this whole fuel thing is going.

One word of caution, if you think this series is going to be a cheater's handbook, think again. With every illegal additive, we'll discuss how tech can uncover it. But if you think this series will help you run faster, you're probably right. Hopefully, once you learn how fuel really works and what all those additives do and don't do, if you're paying attention, you'll probably go faster.

A repeat National Champion once told me that, after years of getting around the fuel rules, trying to pour power into the tank, he discovered that he went faster, with fewer failures, when he ran straight gas and oil. "Every time I tried to juice the fuel and go faster, I hurt myself. And I expect 99 percent of the racers out there do the same." I expect he's right and, in upcoming months, we'll look at why.

Until then, play it straight and concentrate on the things that will really make you faster.

THE QUESTION OF FUEL
PART 2 - Passing Gas the Clean Way

By John Copeland

Last month we talked about some of the factors that influence the way fuel performs in your engine and, consequently, how it makes your engine perform. We talked about octane rating, flame speed, vaporization and a lot of other stuff and, hopefully, we didn't lose you in all the technical stuff. After all, all you really want to do is go fast and pass tech, right? Well, this time we're going to look at the passing tech part.

Since the fuel legality issue began, race officials and tech people have spent sleepless nights trying to figure out how to catch the cheaters. They've used baby bottles and fuel "sniffers" and all manners of chemical tests. The oldest test in common usage is the baby bottle test. Before many racers had access to some of the more sophisticated additives, we had methanol.

Add enough methanol to gasoline (less than about 40 percent and you didn't gain anything) and a McCulloch or a West Bend, or a Clinton would really fly. It mixed well with gasoline, and with most oils in common usage at the time. Those of you who started karting after the Digatron meter was introduced in 1983 probably have never seen this test performed, but it really works.

You see, while methanol is soluble (it mixes well) in gasoline, it is even more soluble in water. Add to that the fact that gasoline doesn't mix at all with water and you've got yourself the makings of a way to detect methanol in gasoline. All the tech man has to do is take a sample of fuel and put it in a container with volume markings on it.

You could use a fancy graduated cylinder, or a measuring cup for that matter, but we mostly used baby bottles because they were cheap, had screw on caps, and were readily accessible. Anyway, you put a fuel sample in the baby bottle and you note the volume, say 4 ounces. Then you add an equal amount of water and shake gently. When the mixture settles down in the bottle, the water will be on top and the gas and oil mixture will be on the bottom. Since you put in 4 ounces of fuel and 4 ounces of water, the dividing line between the two should be at the 4 ounce mark. But remember, methanol is more soluble in water than it is in gasoline. In fact, it likes water enough more than gas that it will leave the gasoline and dissolve in the water. If your 4 ounce fuel sample is 25 percent methanol, when the fuel/water mixture in the bottle settles out, there will only be about 3 ounces of gasoline on the bottom and 5 ounces of water/methanol mix on the top. Pretty neat, huh?

It was messy, and it took some time, but it worked pretty well, and it still does. The baby bottle test is still a pretty good way for 4 cycle tech guys to spot stuff in the methanol that's not supposed to be there. Of course, in that case, you expect to see all the fuel absorbed into the water. Anything that doesn't, probably isn't supposed to be there in the first place.

With the introduction of the Digatron Fuel Meter, fuel checking went high tech. What the meter actually measures is called the "dielectric constant" of the sample. Some folks mistakenly think that the dielectric constant and conductivity are the same, but they are very different. Conductivity is the ability to pass an electric current between two electrodes and is measured as 1 /resistance with a direct current. Dielectric constant is a measure of capacitance measured with an alternating current. While both distilled water and iso?octane have very low conductance, the dielectric constant of distilled water is 80 and isooctane is 1.94!

Anyway, the Digatron meter measures the dielectric constant of the fuel sample. The national tech officials have specified that the meter be calibrated to ?55 with the probe immersed in cyclohexane, which has a dielectric constant of 2.023. After this calibration, the probe is immersed in the fuel sample and it may not read 0.0 or higher. Additives like alcohols, Propylene Oxide, or others tend to align themselves with an electric field (chemists say they're "polar") and they have higher dielectric constants. It only takes a drop or two of these rascals to make the meter read in the positive range and you're illegal. Setting the meter at ?55 gives you plenty of room for minor variations in gasoline composition or for different oils, but it will blow the whistle on most of the funny stuff.

By the way, while we're on the subject of the fuel meter, it is very important that the person doing fuel tech do it right, or he may end up tossing out innocent competitors. After the meter is calibrated, there is no need to put the probe back into the cyclohexane between every reading. In fact, doing so will mess up the calibration, because every time you take the probe out of the fuel tank and put it back into the cyclohexane jar, you dilute the cyclohexane with gasoline. You keep adjusting the meter for this contaminated cyclohexane and the calibration goes straight to "you know where." It's only necessary to re-immerse the probe and check the calibration if the reading comes up illegal. Then it's a good idea to recheck the meter and recheck the fuel.

The Digatron meter is very effective at detecting polar compounds used as additives, but there are two important shortcomings with this method. First of all, there are some chemicals that folks are experimenting with in their fuel that are non-polar, or that have a dielectric constant close enough to legal gasoline that the meter may not spot them. Some competitors have also found ways1to use material with low dielectric constants to mask the presence of other additives with higher constants.

Fortunately, only a few karters have the knowledge to circumvent the rules in this manner, and fewer still are desperate or dishonest enough to do so. A larger concern for the reliability of the Digatron meter is that the oil companies' never-ending search for more mileage and fewer emissions has led to the addition of a host of new components to readily available pump gas. Some of these components may alter the dielectric constant of the fuel enough to read over 0.0 on the meter. No tech man wants to see an innocent competitor tossed out because the fuel he or she purchased had something in it that it shouldn't have. The problem is that the poor tech man has no way of knowing whether the fuel fails the meter because of something the oil company put in it or something the karter put in it.

There is another way, however, to use the Digatron meter, and it borrows somewhat from the "baby bottle test" as well. If we take a fuel sample and add a roughly equal amount of water to it, then agitate it, like in the baby bottle test, we should get two clearly separated layers of liquid in the container, water on top and fuel on the bottom. Then take a reading with the Digatron meter on the fuel portion of the fuel/water sample and a reading on the fuel-only sample from the tank. If nothing has migrated from the fuel to the water, the meter readings should be exactly the same. However, if the fuel contains anything that leaves the fuel to dissolve in the water instead, the reading of that fuel will be different than the fuel that was not exposed to water.

It's probably a good idea to allow five points of leeway, plus or minus, on the reading to allow for any minor absorption of elements in the oil, but anything more than that is an excellent indicator that something is in the fuel that shouldn't be there. This test won't be able to tell you who (oil company or karter) put whatever in there, but it's a reliable test for most of the commonly used illegal additives.
Finally, there are now, and have been, a number of chemical reaction tests for various illegal additives. Most involve adding a sample of fuel to a test tube containing some chemical. Tech officials must then look for some specified reaction, such as a color change or bubbling. If properly designed and performed, these reactions can provide undeniable proof that the specific additive is present. The problem is, most tests like these require controlled conditions, or very accurate measurements of quantities, or experienced personnel to interpret them.

Unfortunately, we rarely have any of these things at the track, conditions are marginal, it is impossible to measure quantities accurately enough, and we lack trained, experienced technicians to perform and interpret the tests. Furthermore, many of the chemicals required for tests like these are dangerous in their own right. Acids and hydrides are commonly used for detecting specific hydrocarbons, and both families of chemicals may react dangerously with unexpected ingredients in fuel, or even with water! As an additional test, and in the hands of trained, experienced personnel, they can provide a valuable additional tool for the fuel-tech man. But in the wrong hands, or under the wrong conditions, they can be more dangerous than the fuel additives they were designed to find.

Next month we'] l start looking at specific additives and what they do. We'll also discuss how to spot them in tech. We'll probably end up doing some basic chemistry along the way, but 1 hope that you'll bear with me and see where this whole fuel thing is headed.

THE QUESTION OF FUEL
PART 3 - Pre-ignition, Detonation Different in Many Ways

By John Copeland

Welcome to the third installment in our series about fuel. As 1 said at the beginning, the whole point of this series is to try to demystify the subject of fuel and fuel additives. Of course, this really applies primarily to the gasoline classes, although I'm told that some Briggs racers have been rumored to add a drop or two to their methanol when the pump-around wasn't being used. The fact is, there are a list of things that will burn as fuel in your engine as long as this page, or longer. I'm sure you've heard of a lot of them, and some you haven't. But all you amateur fuel chemists out there can't hold a candle to the high-powered research going on at oil companies all over the world, both for improved pump gas and for better racing fuel.

True confession time: This project is turning out to be a lot more complex than I ever dreamed. A lot of you have written or called to offer encouragement and information. I've also received dozens of reprinted articles and faxes with additional information to work into upcoming articles. This is a subject of global proportions and I've spent the last few weeks reviewing literature from petroleum industry publications, racing magazines, all sorts of resources. To all of you who have taken the time to read the first two articles and sent more material for me to review, my greatest thanks. Keep it coming! As long as there is more to report on the subject, I'll keep after it.

Whoever said, "No good deed goes unpunished" must have been a writer. I know 1 always chuckled at the letters to car magazine editors pointing out errors in print. Now the shoe is on the other foot. In the first installment (November '94) 1 referred to pre-ignition as another term for detonation. Boy did I hear about that! Let me make this very clear. While they are similar in some respects, in many important ways, detonation and pre-ignition are very different. Both are very destructive conditions and both are the result of combustion initiated by some force or condition other than the firing of the spark plug.

Pre-ignition is the ignition of the fuel/air mixture in the cylinder, prior to the firing of the plug, most often by a "hot spot" in the cylinder, the head, on the piston assembly or on the plug itself. It can be a carbon buildup, an overheated spark plug electrode, or a sharp bit of metal, like you might get in the head if the engine "swallowed" something and dinged up the top of the piston and the head.

This premature ignition generates intense heat, not only from the combustion itself, but because the combustion happens earlier in the compression stroke than it should and the rapidly expanding hot gasses are subjected to additional compression, generating more heat. The only good news here is that pre-ignition generally shows up pretty quickly as rapidly climbing cylinder head temperature. You may not always be able to hear pre-ignition, but, if you run a cylinder head temp it's hard to miss the warning signs.

Detonation, as so many of you correctly pointed out, is an entirely different animal. Detonation occurs when the fuel/air mixture ignites from the combination of heat and pressure within the cylinder during compression. Like pre-ignition, this ignition occurs independent of the spark plug firing, but, unlike pre-ignition, it can and does occur after the plug has fired. The existing heat in the cylinder and head, combined with the rapidly rising pressure as the fuel/air charge expands from the spark ignition, exceeds the fuel's ability to resist spontaneous combustion, and it explodes. The result is the collision of two independent flame fronts and the results are violent!

You've probably heard your car or truck "ping" on a hard pull when its in too high gear. Well, that's detonation. Just as thunder is the collision of two air masses after a bolt of lightning separates them, detonation is the collision of two expanding gas masses. This is thunder in your cylinder, so to speak, but much more destructive. If you can't hear it over the noise of your engine, and it goes on for very long, the results will be expensive. Often there is no significant rise in head temperature, but if you use an exhaust gauge, you may see a drop in EGT. Detonation exerts tremendous physical forces, as well as thermal ones, and it can break pistons, destroy ring lands, break rings and even lead to bearing failure.

Detonation is of particular interest here because it is directly related to fuel quality. As we discussed before, octane rating is a measure of how well a particular gasoline will resist detonation. It is measured as a comparative figure to iso-octane, which is defined as having a 100 octane rating. While most engines in popular use in karting have relatively low compression, there are still conditions under which detonation may occur and that means you'd better fuel up with enough octane to resist that detonation. However, remember from our earlier discussion, higher octane generally means slower flame speed, and that's not particularly good in our application.

Long tracks, both enduro and some longer sprint tracks, call for numerically short gear ratios, sometimes as low as 4:1 . That means your engine is going to be lugging a lot more than if you piled on gear and over-wound it down the chute. Add to this the fact that most drivers set their carb settings on the straightaway when the engine is approaching top end and engine loading is actually decreasing, and you end up with a lean condition in the midrange, right where the engine is doing all that lugging. Now factor in the increasing trend to shorter and shorter pipe lengths and the resulting scavenging of the cylinder by the exhaust pulse, and you have a great recipe for detonation (Note: to those of you using a slippery pipe, pulling it too soon or too fast has the same effect and wins you a quick ride on the detonation express). The key factor here is the lean condition in the mid-range. Unfortunately, most head temp sensors simply can't respond quickly enough to see this lean condition as you make the transition through it. Exhaust temp can. One side effect of detonation is a rapid drop in exhaust temperature. If the head temp is lower than you'd like and you tweak it in to bring the temperature up, you may inadvertently induce detonation.

With exhaust temp you can see the EGT start to fall and quickly richen up the mixture. There is a lot more to the detonation issue, including head configuration, pipe design, ignition timing and squish band configuration. Al Nunley of Mayko Karting in California has written extensively on the subject and is, perhaps, as knowledgeable as anyone I know. If you want to know more about the mechanics of detonation, specifically as they relate to kart racing, spin back through your old karting publications (I'm not the only one who keeps them forever, am I?), or give Nunley a call.

To combat detonation with fuel octane, you can either use a gasoline that has a higher octane rating by itself, like race gas, or you can doctor up lower octane gas with any number of additives. There are several commercially available add-in octane boosters on the market, and most contain some Tetra-Ethyl Lead or a substitute for it. The problem is, Tetra-Ethyl Lead is the stuff the government made them take out of gas to make unleaded gas in the first place! They keep a pretty tight rein on it and you can't really get what you want from the over-the-counter additives.

Another alternative is to blend your own gasoline with additives that will raise the net octane rating of the fuel. The trick here is to find additives that will do the job without coming up bogus at fuel tech. Alcohols, including methanol, ethanol, isopropyl, tertiary butyl alcohol, toluol and xylol all have octane ratings over 100, but they absorb water, are to some degree corrosive and, here's the kicker, they set the Digatron dielectric meter off, big time.

On the plus side, they have relatively good potential power and combust completely. While they are, of course, poisonous in unburned form (as is gasoline), the combustion products are relatively clean and nontoxic.

Aromatics like toluene, xylene and benzene all have high octane potential, and all are present in some racing gasolines in varying concentrations. They are also poisonous before combustion, but their combustion is not nearly as complete as the alcohols and their combustion products coming out the pipe aren't all that healthy either.

Toluene and xylene are readily available at paint and hardware stores, while benzene (the best of the bunch, octane-wise) is virtually impossible to get in reasonable quantities because of government regulations. Benzene is high on the government's list of carcinogens, as well as being a vital component in manufacturing some illegal drugs, so steer clear of this one!

Analine is another octane booster on the government's "hit list." Like benzine, it's used to manufacture illegal drugs but, maybe more importantly, it's a skin-absorbed poison and is very toxic. As 1 mentioned in an earlier article, the chemicals that you may have heard about somebody using in their fuel are, in most cases, very dangerous. As these articles continue, we'll be sure to note the critical health and safety hazards of each potential additive we talk about.

In upcoming articles we'll be discussing these and a lot of other additives with regard to their potential for improving performance in a karting application. But from the point of view of detonation and the damage that it can cause, alcohols and aromatics have been the traditional routes to try to "jack up" the octane rating of pump gas. All this supposes that you can't get your hands on good old Tetra Ethyl Lead, the "real thing" octane booster-wise. Well, that's not necessarily so. Racing gas has Tetra Ethyl Lead in it, and so does aviation gas. There are even some leaded fuels still available in some areas for agricultural use.

The point is, nothing currently available is as effective at controlling detonation as leaded fuel. It is readily available in a variety of octane ratings, from ratings just above pump gas to ratings over 115. Bearing in mind that you only want enough octane to prevent detonation. you should be able to accomplish that with a well-considered choice of commercially available gasoline. Or, if you choose, you might consider mixing a Proportion of leaded racing gas or aviation gas with a lower octane pump gas to get the performance you need for your particular application.

Just remember, octane does nothing to improve performance in and of itself. All it does is measure the ability of the fuel to resist detonation. And there is some evidence that it inhibits flame propagation (flame speed) across the combustion chamber and, thus, fuel with too high an octane rating may actually reduce engine performance.

Next time we'll talk about the hottest subject in the karting fuel controversy right now: oxygenated compounds. Until then, stick to the straight stuff, either from the pump or from a barrel. It's safer and, in most cases, it will perform better for you. If you have any questions or comments, or if you have information or article reprints that you think would be helpful in exploring this subject, please fax them to me at (317) 742?0935. But please, no more jabs about pre-ignition/detonation.

THE QUESTION OF FUEL
PART 4 - Oxygenators are the 'Hottest' Topic in Fuel Chemistry

By John Copeland

By far the hottest (if you'll pardon the expression) topic in fuel chemistry these days is the subject of oxygenators. In their never-ending quest to formulate cleaner burning gasoline for the general motoring public, the major oil companies are using compounds to improve the combustion efficiency of the gas you can buy at the pump. Unfortunately, the real villain here isn't the gasoline, it's the poor efficiency of today's production automobile and truck engines. Better designed engines, operating at much higher temperatures, would go a long way toward cleaning tail pipe emissions, but, the truth is, it's much cheaper for them to try to fix it in the gas tank.

Oxygenators are, pretty much, just what they sound like: compounds that increase the amount of oxygen available for fuel combustion. You remember from high school chemistry that a fire can't burn without oxygen? Well, it's the same inside your engine's combustion chamber. It needs adequate oxygen to burn the fuel. Unfortunately, in most circumstances, we just aren't getting enough, either because the volume of air coming through the carb (remember, air is only about 20 percent oxygen) isn't sufficient, or because the engine can't manage the heat load that a leaner mixture (one containing more air per unit of fuel volume) would generate. (Refer back to Part 1 of this series for more about fuel/air ratios). Oxygenators are, in general terms, flammable compounds that contain at least a portion of the oxygen they need for combustion as part of their own composition. Gasoline, in its basic, unaltered form, contains absolutely no oxygen. It must rely totally on airborne oxygen for combustion. Oxygenators can enhance combustion by assuming some of the burden of providing combustion oxygen

These compounds have been around for a long time but, for the most part, their use has been limited to applications where their ability to furnish most, or all, of the oxygen for their own combustion meant that they could burn explosively. A good example is Tri-Nitro-Toluene, better known as TNT. But for the purposes of improving the quality of fuel combustion, significantly slower-burning, less unstable oxygenators are the focus of interest.

By far the most widely known oxygenators, and the most widely used in commercial gasolines, are alcohols and alcohol-related derivatives. But the fuel chemists at the oil companies have developed a whole new crop of these compounds in hopes of creating a leaner-burning, cleaner fuel/air reaction. This leaner, cleaner combustion translates, in your car or truck, to better fuel mileage and cleaner fuel chemistry tail pipe emissions. We've all heard about gasohol as a catch-all name for gasoline/alcohol blends. For our purposes, we can pretty well dismiss all these alcohol blended gasolines because we already know that they won't pass the standard digatron meter test. But let's look at some of the other oxygen bearing fuel additives that are finding their way into gasoline. Some of these are being added by the gasoline manufacturers and some are ..., well, let's just say that some are finding their way into kart fuel by other means.

`THE RACER'S CHOICE'

Propylene Oxide (CH3 CHCH2 O) has seen considerable use as a performance enhancer over the years. Even when we didn't know what it was doing, we knew it was doing something good. The fact is, Propylene Oxide does several things that racers like. It is highly volatile, boiling at only 93 degrees Fahrenheit, and has a correspondingly high heat of vaporization. That means that it helps cool the incoming fuel charge, thus improving charge density and improving power output. That helps leech some of the latent heat out of the engine as well. It also brings along some of its own oxygen to the party in the combustion chamber. That means that it helps the rest of the fuel components burn more completely, improving the efficiency. Unfortunately, that additional oxygen tends to make the fuel charge burn with a somewhat higher heat of combustion, releasing more heat into the engine. This can more or less negate the positive heat-leeching effect. And it also puts the higher heat exactly where you don't want it; in the head and on the piston crown. In your car or truck, that higher heat and improved efficiency means fewer tail pipe emissions. On the kart track, it means more bang out of every drop of fuel going through the carb. Here's the downside. Propylene Oxide is bad for you, real bad. It is corrosive in contact with skin, just like battery acid. It is a skin-absorbable poison, fatal at 1,500 milligrams per two kilograms of body weight. And it had been determined to be a Class 3 carcinogen. Even if you are willing to assume the risks of using this material yourself, you are also exposing any competitor behind you to risk from incompletely combusted Propylene Oxide. Don't do it. Anything less than about 8 percent added to gasoline (by volume) has no measurable effect, but any more than about 3 percent will send the digatron meter sailing.

There are a couple of chemicals in the Nitroparaffin family that are of some interest as oxygenators. Methyl Ethyl Ketone (C2
H5 COCH3), often referred to as MEK, appears on the surface to be an attractive oxygenator. A commonly used industrial solvent, MEK has the unfortunate property of consuming all its own oxygen during its own combustion, leaving none to benefit the remaining combustion process. Coupled with its relatively low specific energy, it's basically a waste of time.

The same goes for Acetone (C3 H6 O), whose relatively meager supply of oxygen isn't even sufficient to support its own combustion, much less lend any to the gasoline reaction. Acetone does have one attractive property, however. It is extremely hydroscopic, meaning that it attracts and absorbs water. In the old days, the McCulloch racers knew this and used to mix acetone with their alcohol to help suspend the moisture that the alcohol attracted and put it in a more combustible form. It will do this in gasoline as well and, since water is not soluble in gasoline at all, but acetone, even acetone that has absorbed some water, is soluble in gasoline, it's a good way to deal with water-contaminated gasoline. But there's no power advantage to be had here and, if you're having a problem with water in your gasoline, you don't need a chemical to fix it. You need a better gasoline supplier. By the way, ketones like MEK and Acetone are also really hard on rubber and plastic parts, like carb diaphragms, etc. In concentrations of less than about 15 percent by volume, it is impossible to see any change in the combustion process, while anything over 10 percent may dissolve your metering diaphragm before the day is done. Sounds like a bad bargain.

EXPENSIVE ALTERNATIVE

Nitropropane ((CH3)2CHN02) is a rather expensive nitroparaffin that is, in the right form, about 70 percent as potent as Nitromethane (CH3 N02). I say "the right form" because Nitropropane comes in two forms, called Nitropropane I and Nitropropane 2. Nitropropane I is the most readily available, because it is a sometimesused cleaning solvent. Unfortunately, it is completely worthless as a combustion reactant for our purposes. Nitropropane 2, however, contributes significantly to oxygenation of the combustion process when used in concentrations of 10 percent or more by volume. Its primary hazard is that it is extremely volatile, sensitive to even ignition by static electricity. And, at over $50 per gallon on the open market, few racers will be tempted to mess with it.
The ethers are a family of oxygen-bearing hydrocarbons that have drawn increasing attention from the fuel industry. With a relatively high percentage of oxygen per volume (15 to 18 percent), they bring considerable free oxygen to the combustion process. But unlike the alcohols, they can actually improve vaporization over straight gasoline, while reducing exhaust emission in passenger cars and trucks. The result is what the industry calls "improved drivability" and relates primarily to cold weather starting and cold engine running. Of more interest to us is the higher heat of vaporization and its resulting colder inlet charge and heat leeching, as mentioned above.

The most widely known ether is Ethyl Ether (C2 H5 OC2 H5) and it is the primary ingredient in automotive "starting fluid" sprays. Incredibly volatile, it will vaporize even at sub-zero temperatures and is just the ticket for getting your Chevy started on a bitter cold morning. Thankfully, we don't race in such conditions. For our purposes, Ethyl Ether simply is too volatile; it evaporates too quickly and at too low of a temperature to render it as a useful additive in karting. Besides, Ethyl Ether's telltale odor makes it very hard to hide. One other serious problem with some ethers is their tendency to form unstable, explosive compounds called
Peroxides. These dangerous compounds can develop when ethers are exposed to either heat and/or sunlight, even in closed containers. For the most part, ethers are relatively safe, healthwise. Like any other hydrocarbon, of course, they are harmful or fatal if
swallowed, but most members of this chemical that we are likely to encounter in fuels are relatively safe.
A very important exception to the previous comment is a material called Diethylene Ether H8 02), or more commonly referred to as Dioxane. With twice the oxygen per molecule of Ethyl Ether, it would seem to be an attractive oxygenator. PLEASE READ THIS! DIOXANE IS A VERY POWERFUL SKIN-ABSORBED POISON AND KNOWN CARCINOGEN. It is neither safe to handle, nor to breathe, nor to be around in any way. Its combustion products, in the form most likely to be emitted behind a kart, are also poisonous and carcinogenic. This is nothing to fool around with! Anyone foolish enough to monkey with this material has no business on the racetrack and no business in the sport! There is also a compound called Dioxine, but it is of no value whatsoever as a combustion additive, although someone may accidentally refer to Dioxane as Dioxine and vice-versa.

NEW FUEL ADDITIVES

On a happier note, you may have heard about some new fuel additives from the oil companies called MTBE, ETBE and TAME. These are ethers too and the letters stand for Methyl Tertiary-butyl Ether, Ethyl Tertiarybutyl Ether, and Triamyl Methyl Ether. The first two compounds are made by reacting Methanol or Ethanol with isobutylene and all three have found considerable success as gasoline additives, yielding significant oxygen to the combustion process.

The oil companies have seized on MTBE and TAME, and more recently on ETBE, as environmentally friendly ways to enhance octane rating, improve drivability, and "stretch" gasoline through the use of renewable resources. It is unlikely that you would see any significant improvement in engine performance by adding these compounds in quantities beyond what the oil companies are already putting in the fuel, between 15 and 19 percent by volume. The only way to be sure that these compounds are not in the gas you take to the track is, as we've said before, to purchase racing gasoline from a reputable dealer of racing gasoline, from the drum. However, if you wish to experiment with them, and if you can find a resource to provide them, they are reasonably safe to use. Again, 15 to 19 percent is the industry standard. At this point we have not finished the research to determine how these additives will affect the digatron meter or how much will send it over the magic "0.00" mark.

So let's summarize the subject of oxygenators. Given that we can't ever get enough oxygen from the limited amount of air the engine can suck down the carb throat to affect really efficient, complete combustion of the fuel, some oxygenators can provide additional "free" oxygen to enhance the combustion process. The most common of these are the alcohols, but, because of their dielectric properties, they won't get past the digatron meter test at tech. Propylene Oxide and some of the other Nitro-Paraffins are good sources of oxygen, but are corrosive to engine and carb parts, and some of them are very dangerous, health-wise. Ketones are, for the most part, worthless as oxygen sources, as they consume all their own oxygen during combustion, leaving none to improve the combustion of the other fuel. And, finally, ethers can improve combustion and liberate additional heat energy from the fuel, but require such large percentages to achieve the desired results as to be hard to conceal. And Dioxane, an ether, is way too dangerous to monkey around with.

One more thing; the use of oxygenators in air-cooled engines is a particularly awkward juggling act. Remember, we said in the first installment of this series that tests had shown that we use almost 50 percent of the fuel that goes into the engine as a COOLANT. Well, when you bump up the oxygen level of the fuel mixture, whether by adding more air or by adding oxygenators, the heat of combustion and the temperature in the engine will go up accordingly. Oxygenators, in effect, lean out the engine. Given the cooling limitations of the air-cooled engine, the only option is to richen the mixture and there goes any hope of a significant performance advantage. What we're saying is this: There is, most likely, one or more oxygenators already present in any gasoline you can buy at the pump these days. These compounds may cause your fuel to fail the digatron fuel meter at tech. The only way to avoid it is to buy race gas from a barrel. Adding oxygenators to fuel on your own is dangerous, to you and to your fellow competitors. Any performance gain that you might have achieved from the addition of oxygenators to your fuel is, if you use an air-cooled engine, most likely negated by having to run the mixture richer to compensate for the additional heat that the oxygen-enriched fuel generates when it burns.

Hopefully by next month we'll have some testing completed on both the performance effects of the additives we've talked about, and on the necessary tech procedures to spot the guys who are "juicing" their fuel. In the meantime, if you see somebody fiddling with their gas, ask them to stop. If they ignore you, tell the tech man. They're not just cheating, they're taking real chances with their health and with yours.

THE QUESTION OF FUEL
PART 5 - Testing For Performance And Legality

By John Copeland

In the previous four segments of this series, we've discussed the specific factors that influence fuel performance, commonly used fuel tech procedures, and the subject of oxygenators and other additives. Hopefully we've laid the groundwork for this month's subject: the actual test results. We've tested fuels and additives, both for performance and for legality.

Before we get to the subject of additives, a few words about the current state of fuel legality. As we discussed earlier, the oil companies have been reformulating their products in the effort to improve fuel mileage and reduce tailpipe emissions. In most cases, this reformulation has involved adding Ethers like MTBE or ETBE, and the federal government has dictated that only reformulated gasoline may be sold in major metropolitan areas. To check this out and to determine if karters buying their fuel in major cities might be at risk, legality-wise, we obtained samples of nine pump gasolines from Chicago area gas stations. We then obtained samples of the same nine pump gasolines from stations here in Lafayette, Ind. In addition, we also tested samples of six racing gasolines from several geographical sources. We mixed each of these gasoline samples with Burns oil at a ratio of 20:1, mixing 4 ounces of Burris Castor and 2 ounces of Burris Blend per gallon of gasoline. All fuel samples were tested at 55 degrees Fahrenheit and, of course, the Digatron meter was calibrated to -55 with Cyclohexane. (See chart #I for the results:)
Two things are pretty obvious here. First of all, fuel legality is highly variable, both from manufacturer to manufacturer and from grade to grade. Secondly, obviously the composition of the fuels sold in the Chicago area are not the same as those sold in the Lafayette area, at least not at the time these samples were purchased. As we've said before, race gas is much less subject to changing composition. You should expect that any of the race gases listed here will test approximately the same as our results here.

The test procedure was as follows: the Digatron meter probe was immersed in a measured quantity of base fuel. Then the additive being tested was slowly added to the base sample until the meter reading exceeded 0.00 or until it became apparent that the testing would not exceed the 0.00 mark. At that point, the percentage by volume of the additive being tested was calculated to determine the threshold of legality for that particular additive. Here are the results:

Chart #2

Percent by Volume

Meter Reading
Propylene Oxide 1.75% +1
Nitro Methane 0.80% +1
Nitro Propan 0.20% +6
Ethyl Ether 0.73% +1
Toluene 59.00% -8
Xylene 58.00% -8
1,4 Dioxane 70.00% -26
Hi-Rev 3:1 30.00% -28
Klotz Coxoc 40.00% -30
To help you interpret these results, 1.00 percent by volume is 1.28 ounces per gallon, or about one tablespoon of additive per gallon. From these results we can determine that it is extremely unlikely that a fuel mixture could pass the meter and contain enough Propylene Oxide, Nitro Methane, Nitro Propane, or Ethyl Ether to accomplish any measurable performance gain. It is also apparent that the Digatron test is insufficient to detect significant quantities of the other flue additives tested. Obviously, other testing procedures will be required to detect these.

In the second installment of this series (December 1994) we outlined a test using a combination of water absorption and the Digatron meter. In this test, two fuel samples are taken and, to one sample, an equal volume of water is added and the mixture gently agitated. When the agitated sample mixture is allowed to settle, the fuel portion of the mixture will be separated from the water portion, with the fuel portion on top. Digatron meter readings are taken from the fuel-only sample and from the fuel portion of the fuel-water sample. The readings should be the same. In the event, however, that an additive or additives are present that are more soluble in water than in gasoline, the relative meter readings will be different from one another. Allowing for some minor variances, any deviation of more than five points on the Digatron meter would indicate the presence of something in the fuel other than what the manufacturer put there. In this test, the base fuel was Unocal race gas, again mixed 20:1 with Burris oil. To each sample we added 10 percent by volume of each additive to be tested, then the test was performed. (See Chart #3 for results:)
Chart #3

There is a third test worthy of consideration that has come to our attention since the second segment of this series was written. We are indebted to Art Verlengiere of RLV and Mark Weaverling, the highly regarded West Coast karting innovator, for sharing their experience with this test with us. The testing procedure is relatively simple, although it requires more accurate measurements and a careful procedure.

Exactly equal amounts of the sample fuel, water and straight methanol are combined in a graduated cylinder or other accurately calibrated container. The methanol will completely dissolve in the water, but the fuel will separate and rise to the top. Once the fuel has separated from the water and methanol solution, the line of separation should be exactly at a point two-thirds up from the bottom of the container.

The use of an accurate graduated cylinder of at least 100ml capacity is recommended, allowing use of 30ml samples of each item. In this case, the separation line between the fuel portion of the mixture and the water/methanol portion should be exactly at 60ml from the bottom, leaving the fuel portion at exactly the 30ml that were originally added. Any reduction of this 30ml volume would indicate the presence of some additive that has left the fuel and gone into solution in the water/methanol solution. For our test, we again used Unocal race gas as the base fuel and used 20 percent of each additive being tested. (See chart #4 for results:)

Chart #4

Percent by Volume

Resulting Fuel Volume
No Additives 0% 30ml
Propylene Oxide 20% 25ml
Nitro Methane 20% 29ml
Nitro Propane 20% 22ml
Ethyl Ether 20% 30ml
Toluene 20% 28ml
Xylene 20% 30ml
1,4 Dioxane 20% 22ml
Hi-Rev 20% 31ml
Klotz Coxoc 20% 25ml
As you can see, this test does a good job of picking up some of these additives, particularly the Nitro Propane, 1,4 Dioxane and Klotz Coxoc. While it's a little more difficult to do this test, it's another valuable weapon in the tech man's arsenal and its occasional use should help deter fuel tampering.

As this is written, we are in contact with tech officials at the National Hot Rod Association, International Hot Rod Association, and the U.S. Powerboat Association, all exchanging information about gasoline tech inspection and sharing ideas to help police this area. We'll pass along any new developments as they become available.

We've pretty well used up our space for this month, but don't despair. Next month we'll have specific test results on the performance of using the various additives we've discussed here. We'll give you actual dyno results from using each of these products, vs. unadulterated race gas. Hopefully we'll see just what you can expect to gain from using these additives. But you'll have to wait until next month for that.

THE QUESTION OF FUEL
PART 7 - Tech Procedures Revisited

By John Copeland

Last month we finally got the awful truth; if someone really wants to cheat with their fuel, they can, and the odds are, they'll get away with it. But how can the honest racer help keep the playing field level? How can you and your club keep fuel cheating under control? Let's start by getting a couple of things clear. Like it or not, legal fuel will always be defined as fuel that will pass whatever test is being used. That means that, whatever it says on paper, if you or your club or track don't tech fuel, then fuel is open! Likewise, if you don't tech it the same way every time, you jeopardize the credibility of the tech. It is critical that the fuel tech be thorough, properly done, and fairly administered. Too many times tech people, even at the highest levels, have gone "headhunting" for a person whom they believe was cheating with their fuel. And their claims that the selection of who was to have their fuel checked was completely random, when everybody knew better, only made them look foolish and diminished the credibility of the whole process. We've already covered several fuel tech techniques in an earlier article, and we have a few more we'll share with you shortly, but first, let's look at the right way to use the Digatron meter.

We've all had our fuel checked with the Digatron meter lots of times, and it seems like every tech man does it different. But, hey!, if my fuel checks OK who cares how he does it? Well, you ought to care, because if the tech man isn't using the right procedure, you may be racing at an unfair disadvantage to a fuel cheater who slipped past the tech man because the testing procedure was wrong. Here's the way to do it right.

1. Turn on the meter and immerse the probe in cyclohexane. The cyclohexane should be in a plastic container, not glass. I know that Digatron supplies little glass bottles with the deluxe fuel testing kit, and they're real handy, but they can affect the meter readings. Always use plastic containers.

2. Allow the meter to "warm up" for at least, five to 10 minutes before setting the knob to read -55. If you just turn it on and start taking reading:. it will "drift" on you a bit. By the way, when you are "zeroing" the meter at -55, hold the probe in the middle of the container of cyclohexane, away from the bottom or sides. Something called the "Adjacency Affect" can change the meter readings if the probe is too close to the sides or bottom of the container.

3. The prescribed -55 setting is presumed to be at 60 degrees Fahrenheit. Temperature change will change the meter readings. The temperature of the fuel sample being tested and the cyclohexane standard must be about the same. A temperature difference of five degrees or more will make a measurable difference in the readings. When in doubt about fuel sample temperature, take a sample of the fuel to be tested, and let it sit next to the cyclohexane sample for about 10 minutes. Just be sure to put the fuel sample in a tightly sealed container so you don't lose anything to evaporation.

4. The meter should be re-calibrated every 30 minutes or so, to compensate for any "drift" in the zero point and to keep everything right. But here's where lots of folks mess up: Once the meter is calibrated, it is not desirable to re-immerse it in the cyclohexane after every fuel sample is checked. Doing so only dilutes the cyclohexane with random fuel carried back into the container on the probe. As the day goes on, the standard on which you are basing your testing will change. Not good. Instead, after each fuel is tested, gently shake any excess fuel off the probe and blot lightly with a paper towel.

5. Periodically clean the probe with aerosol brake cleaner and allow it to dry completely. This product will evaporate completely and will not contaminate the next fuel sample. It is important to clean the probe occasionally because some of the oils in use may remain on the probe after the gasoline has evaporated. In most cases this is not a problem, but sometimes it can bite you.
6. Just as when you "zeroed" the meter in the cyclohexane, when you take a reading on a fuel sample, don't let the probe get too close to the sides or bottom of the tank. Otherwise the "adjacency affect" may change the readings. If a competitor does not have enough fuel to take a good reading in the tank, then he or she is obliged to draw a sample through the fuel line to the carb into a smaller container for testing. Of course, according to the rules, if a competitor cannot produce enough to be properly tested, the tech man is required to disqualify them.

7. In the event that you find a fuel sample that does not pass the meter, that is, one that reads + numbers, immediately stop testing, clean the probe as described above, and recalibrate in cyclohexane. The test again. Fuel that fails under these circumstances should be considered illegal.

8. Moisture in the fuel will shift the meter in a positive direction. Rainy days, or even high humidity can cause fuel to come up illegal. Unfortunately, the rules do not allow for the tech man to vary the definition of legality just because it might have rained the night before! (Racers beware! I once saw a man lose a National event because he left his fuel in the kart tank overnight the fright before the race and it picked up enough moisture to fail fuel tech the next day!)

9. In cases where a fuel sample reads illegal (or suspiciously low) on the meter, you may request that a sample of the oil in use be mixed with a known legal gas. While it does not affect the immediate question of legality of the racer's fuel for that race, it may help identify whether the problem is in the fuel or in the oil.
Using this procedure, the same way, every time, will insure that fuel tech is fair and consistent. Now on to other issues.

Those of you who read Part Six of this series (NKN September 1995) will recall that there are some fuel additives that generate some performance improvements and some that we did not have adequate information on to draw any conclusions. And if you remember Part Five of the series, you'll remember that not all these additives show up in testing with the Digatron meter. Even the water/Digatron test and the 30/30/30 test are not as definitive as you might like: in some cases. Among these additives is 1,4 Dioxane, a very hazardous chemical. Among other things, 1,4 Dioxane is a carcinogen, and a skin-absorbable poison. This is nothing to fool around with! While 1,4 Dioxane will slide past the Digatron meter, there is now a definitive test to identify it in the field. We are indebted to the good folks at Precision Automotive Research, to the National Hot Rod Association and particularly to a company called Germane Engineering in Provo, Utah for their work in developing a positive field test for 1,4 Dioxane. The test is a simple chemical reaction done with materials supplied by Germane Engineering and is available to bonafide sanctioning bodies and their tech people. It requires a few, easily obtainable supplies, and some care in handling, but the test itself is simple and relatively foolproof. Here's how it works:

1. Draw a clean fuel sample from the competitor's tank and put in a small test tube. Disposable eye-droppers work really well for this and are available very cheaply at any laboratory or medical supply. These are also known as disposable pipettes. The test tube should be no larger than l0ml capacity to be easily readable. Five ml size is ideal. These too are cheap and easy to obtain.

2. The test tube containing the fuel sample should be about 1/2 to 3/4 full. This will give the person doing the testing a clear view of any reaction. It's a good idea to write the kart number right on the test tube before doing the test to avoid any confusion.

3. Always wear rubber gloves when using the test reagent from Germane Engineering. It is a strong acid of some sort and you definitely don't want to get any on your hands.

4. Hold the test tube by the bottom so you can get a clear view of what happens in the fuel sample and carefully squeeze ONE DROP of the Germane reagent into the top of the test tube.

5. As soon as the reagent hits the fuel sample, the oil in the fuel will drop to the bottom of the test tube. THIS IS NOT A POSITIVE TEST!

6. If, however, a white or light brown precipitate forms (like little snowflakes) at the point where the reagent hits the fuel sample, and it drifts down through the fuel, THAT IS A POSITIVE REACTION FOR 1,4 DIOXANE! Any fuel sample producing such a reaction should be considered illegal and the competitor disqualified.

7. Used test tubes and eye-droppers should not be re-used and should he properly disposed of. Always use new test tubes and droppers for each new test.

Again this test was developed for the National Hot Rod Association by Germane Engineering under license from NHRA and they alone own the rights to it. Test materials are available only to bonafide sanctioning bodies and only when accompanied by a strict non-disclosure agreement. Any organization wishing to make use of this important testing tool should contact Germane Engineering b_________________Buy it used, buy it cheap and have fun!